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REVOLUTION IN THE MAKING

From STORAGE Magazine Vol 6, Issue 8 - October 2006

As the Internet and related activities continue to expand, the amount of data that needs to be stored is equally in growth. Enterprises and other organisations are increasingly requiring effective ways to store and maintain this data. Bob Aitchison, senior regional manager, EMEA, Qlogic, offers some insights

In recent years, many businesses have seen significant increases in data volumes produced. This data growth has been especially notable in Web-based and e-commerce environments. An example would be email, which impacts worldwide storage by producing more data than is generated by new Web pages. These types of traffic are typically multimedia intensive. Email and Internet-related enterprise/commercial transactions combined have caused a dramatic increase in storable data moving across Internet Protocol (IP) networks.

A new method is needed to bring improved storage capabilities to IP networks and reduce limitations associated with Fibre Channel SANs. The solution, as is widely known, is Internet Small Computer Systems Interface (iSCSI) or SCSI over IP. But what does this new technology mean to your storage environment?
iSCSI Storage will revolutionise the way data is moved, created and backed up. The shift towards iSCSI storage products started in 2004 when the first generation of technologies started to ship. iSCSI or IP storage utilises the benefits of two major connectivity technologies that have each been around for more than 20 years - SCSI and TCP/IP - by combining the two to create the iSCSI or IP storage standard.

iSCSI is an IP-based storage networking standard for linking data storage facilities. By carrying SCSI commands over IP networks, iSCSI is used to facilitate data transfers over intranets and to manage storage over long distances. The iSCSI protocol is among the key technologies expected to help bring about rapid development of the storage area network (SAN) market by increasing the capabilities and performance of storage data transmission. On account of the ubiquity of IP networks, iSCSI can be used to transmit data over local area networks (LANs), wide area networks (WANs) or the Internet, and can enable location-independent data storage and retrieval.

How it works
ISCSI works along similar principles to Fibre Channel, in that SCSI commands and data are 'encapsulated' within transmission packets that are transmitted serially over Ethernet. For iSCSI, this means multiple encapsulation layers within the standard Ethernet Packet (see the diagram over the page).

First, the data and SCSI Command Data Block (CDB) are encapsulated into an iSCSI packet, which is then further encapsulated into a Transmission Control Protocol (TCP) packet. TCP keeps track of the packets into which a block of data is divided, and guarantees delivery and correct sequencing of the packet stream. The final encapsulation is the Internet Protocol (IP) layer - a bit like a postal address system for the network.

The packet and any associated packets are then transmitted over a standard GigE Ethernet network either to a storage device or to a host system. Each layer is then stripped off to reveal the SCSI CDB and data.

Building an iSCSI SAN is no longer limited to those who can manage the complexities and cost of Fibre Channel technology. With the introduction of the iSCSI protocol, any enterprise that uses standard Ethernet technology can now build iSCSI SANs and reap their benefits. Defined and supported by industry-leading storage and networking companies, this new networking protocol that enables low-latency SCSI 'blocks' to be transported via Ethernet and TCP/IP.

SCSI is a new networking - data storage protocol that combines SCSI data blocks with Ethernet IP packets. SCSI commands are encoded in to Ethernet packets and then sent over Ethernet networks. When they reach their destination, these packets are separated out, using the off-load engine into Ethernet and SCSI commands, and the data is then sent to the relevant device.

As iSCSI uses existing Ethernet switches, cables and routers, the deployment costs are much lower than if you were to design a Fibre Channel SAN. Operating systems see iSCSI-connected devices as SCSI devices and are unaware that the SCSI device connected to the network resides across the room or across town.

ISCSI-supported SANS
iSCSI is fully supported by IBM, Microsoft, Cisco and many other major technology players. It takes storage commands directly from the server and transports them over IP to the storage device. However, the performance of this approach is limited and in no way meant to replace SANs based on Fibre Channel. It is targeted at the low end of the market.

iSCSI is a way of extending the core SAN out to the IP network to include low-level servers, which are not typically included in Fibre Channel. This should open up SAN functionality to a whole new generation of servers. According to Gartner Dataquest, by 2006 iSCSI will connect nearly 1.5 million servers to SANs, making it the most widespread SAN technology in use.

The key strength of iSCSI is that it uses the standard NIC card for the processing, but this limits the performance because of the extra processing that the standard requires.

iSCSI will attach to the FC-based SAN through gateways. Vendors are addressing this by including iSCSI and FCIP support in their SAN switches. The Yankee Group has identified entry-level IP storage arrays as a potent source of growth for the networked storage market and will shift the market from mostly Fibre Channel SANs to IP storage systems.

Reduce your storage costs
Using iSCSI allows businesses to get a handle on storage expenses, without refitting their existing network infrastructures. IT managers need to design a storage strategy that couples cost with overall system management and longer-term objectives. The feature set for iSCSI SAN often includes centralised management with easy-to-use interfaces and remote access. Businesses can now justify costs of implementing a storage system with no-single-point-of-failure design, availability (99.999% uptime), scalability, and enterprise-level storage management and protection features.

Installing an iSCSI SAN is affordable for most small to medium businesses (SMBs) today. Most storage experts agree that an iSCSI SAN will cost 30% to 40% less than DAS and 40% to 50% less than a Fibre Channel SAN.

So what's stopping businesses from consolidating DAS systems into an iSCSI SAN? This new technology should not be a factor for businesses not to proceed. The technology has been around for several years and the standard was ratified in 2003. Many of the Fortune 500 have now installed iSCSI SANs as a part of their tiered storage systems.

iSCSI storage systems have joined Fibre Channel solutions for primary storage applications in larger enterprises. These systems are now serving data to business-critical applications, such as email, enterprise resource planning, customer relationship management and online transaction processing systems.

Although there have been some concerns about speed and security with iSCSI SANs, these have all been unfounded - similar to the myths about the speed of iSCSI versus Fibre Channel. Once people are educated, they understand the technology better. Similarly, IT managers sensitive to IP security on corporate LANs overcome concerns once they understand the technology and capabilities to secure iSCSI.

When looking at a long-term view of iSCSI as a storage media, it is unavoidable that it will play a major role in storage consolidation strategies. iSCSI is too prolific not to be successful as a storage transport. ST